Process for the preparation of sulfentrazone

Abstract

The present invention provides a process for the preparation of N-[2,4-dichloro-5-[4-(difluoromethyl)-4,5-dihydro-3-methyl-5-oxo-1H-1,2,4-triazol-1-yl]phenyl]methanesulfonamide (I) which comprises reacting 2-(5-amino-2,4-dichlorophenyl)-4-(difluoromethyl)-2,4-dihydro-5-methyl-3H-1,2,4-triazol-3-one (II) with methanesulfonyl chloride in the presence of a catalytic amount of a source of soluble halide.

What is claimed is: 
     
       1. A process for preparing N-[2,4-dichloro-5-[4-(difluoromethyl)-4,5-dihydro-3-methyl-5-oxo-1H-1,2,4-triazol-1-yl]phenyl]methanesulfonamide (1) comprising reacting 2-(5-amino-2,4-dichlorophenyl)-4-(difluoromethyl)-2,4-dihydro-5-methyl-3H-1,2,4-triazol-3-one (II) with methanesulfonyl chloride in the presence of a catalytic amount of a source of soluble halide at a temperature of from 80° to 140° C. with or without a solvent. 
     
     
       2. The process of claim 1 wherein the temperature is 100° to 120° C. 
     
     
       3. The process of claim 1 wherein the source of soluble halide is selected from the group consisting of quaternary ammonium salts, quaternary phosphonium salts, salts of tertiary amines, salts of basic nitrogen containing heterocycles and salts of arylamine II. 
     
     
       4. The process of claim 3 where the halide is chloride. 
     
     
       5. The process of claim 1 wherein a solvent is used. 
     
     
       6. The process of claim 5 wherein the solvent is toluene. 
     
     
       7. The process of claim 3 wherein a solvent is used. 
     
     
       8. The process of claim 7 wherein the solvent is toluene. 
     
     
       9. The process of claim 2 wherein a solvent is used. 
     
     
       10. The process of claim 9 wherein the solvent is toluene. 
     
     
       11. The process of claim 4 wherein a solvent is used. 
     
     
       12. The process of claim 11 wherein the solvent is toluene. 
     
     
       13. The process of claim 1 wherein the source of soluble halide is a salt of a tertiary amide. 
     
     
       14. The process of claim 13 where the halide is chloride. 
     
     
       15. The process of claim 13 wherein a solvent is used. 
     
     
       16. The process of claim 15 wherein the solvent is toluene.